Quick-change field coil assembly for use in an electrode having a fluid-cooled arcing surface

ABSTRACT

An electrode has a detachable tip secured to a supporting column. The column includes fluid-channeling and electrically conducting tubes, electrically insulated from each other, extending at least a portion of the way therethrough toward the tip. Within the removable tip is a detachable magnetic field coil assembly including conduit extensions which, when the coil assembly is inserted in the electrode, are aligned with the tubes respectively. Male fittings engage contact finger assemblies and make good electrical connection. The fittings may be on the tubes and the contact finger assemblies may be on the conduit extensions, or the fittings may be on the conduit extensions and the contact finger assemblies may be secured to the ends of the tubes. Means carried by the column, or the conduit extensions including fittings or finger assemblies thereon, or both, provide fluidtight seals for the cooling fluid flow circuit through the magnetic field coil.

United States Patent 1 3,580,977

[72] Inventors George A. Kemeny 3,194,941 7/1965 Baird 1. 219/121 E t;3,369,067 2/1968 De Corso.. 13/18 Charles B. Wolf, Irwin, Pa. 3,369,0682/ 1968 Kienast 13/18 [21] Appl. No. 12,269 3,369,069 2/1968 Kemeny etal. 13/18 [22] Filed Feb. 18, 1970 3,385,987 5/1968 Wolfet a1. 13/18[45] Patented May 25, 1971 3,392,227 7/1968 Ostberg 13/18 [73] Ass'gneey zgaggz g Col-Porno Primary ExaminerBernard A. GilheanyContinuation-impart of application Ser. No. jij' Emmmer Roy Ema!777,366, Nov. 20, 1968, now abandoned. 0rneysA. T. Stratton, C. L.Mcl-lale and M. 1. Hull ABSTRACT: An electrode has a detachable tipsecured to a l 54] QUICKCHANGE FIELD COIL ASSEMBLY FOR supportingcolumn. The column includes fluid-channeling and USE IN AN ELECTRODEHAVING A FLU) electrically conducting tubes, electrically insulated fromeach COOLED ARCING SURFACE other, extending at least a portion of theway therethrough 19 Claims 2 Drawing Figs. toward the tip. Within theremovable tip is a detachable mag- [52] U 8 Cl 15/18 netic field coilassembly including conduit extensions which,

when the coil assembly is inserted in the electrode, are aligned [S 1Int. Cl with the tubes respectively Male fitti engage Contactfmgelassemblies and make good electrical connection. The fittings 13/ 1may b on the tubes and the Contact fi assemblies may be 18; 219/121(CF), 145 on the conduit extensions, or the fittings may be on the con-[56] References Cited duit extensions and the contact finger assembliesmay be secured to the ends of the tubes. Means carried by the column,

[50] Field of Search UNITED STATES PATENTS or the conduit extensionsincluding fittings or finger assem- 2,858,4l2 10/ 1958 Kane et a] 219/121 blies thereon, or both, provide fluidtight seals for the cooling3,130,292 4/1964 Gage et al 2 19/12 1 (X) fluid flow circuit through themagnetic field coil.

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V 4a l7 26 102 5a 39 27 40 I8 20 I 33 7 I 4 I3 I4 i ,2:- 4 T' PatentedMiiy 25, 1971 FIG.2.

QUICK-CHANGE FIELD COIL ASSEMBLY FOR USE IN AN ELECTRODE HAVING AFLUID-COOLED ARCING SURFACE CROSS REFERENCE TO RELATED APPLICATIONS Thisapplication is a continuation-in-part of application Ser. No. 777,366,filed Nov. 20, 1968, now abandoned and assigned to the assignee of theinstant invention.

This application is also related to the copending application of C. B.Wolf et al. for Electrode Assembly, Ser. No. 7l5,6l9, filed Mar. 25,1968 now Pat. No. 3,480,717 and assigned to the assignee of the instantinvention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to electrodes having tips with fluidcooled arcing surfaces andemploying a field coil within the tip for setting up a magnetic field tocause thearc to move substantially continuously around the arcingsurface, and more particularly to such a structure in which the fieldcoil is composed of hollow conduit through which a cooling fluid flowsand an energizing current flows and which may be quickly removed from asupporting electrode column and a new field coil inserted in the columnin a manner to make good electricalconnection and provide fluidtightseals;

2. Description of the Prior Art Prior art electrodes having a field coilcomposed of hollow conduit through which a cooling fluid flows and whichalso carries a current to set up an arc moving magnetic field utilize astructure in which the field coil copper conductors have tubular leadsbrazed to the field coil copper which extend through the electrodecolumn structure to a suitable exterior point at or near the other endof the electrode where coolant and current connections are made, asexemplified for example in U.S. Pat. No. 3,368,0l8 and U.S. Pat. No.3,368,019. The disadvantage of the prior art arrangement is thatchanging the field coil is a laborious procedure which requiresgenerally in the order of hours. Furthermore, to reducethe time requiredto change field coils it is necessary to storezfield coils with longlead attachments which for some electrodes result in a foot-longassembly, which is difficult -to;store and difficult to handle.

SUMMARY OF THE INVENTION In our invention the electrode tip includesinner and outer shells with peripherally spaced U-shaped tubestherebetween forming fluid passageways, the shells and tubes beingbrazed together to form a unit. The tip assembly may be removed simplyby unscrewing the outer shell from the supporting column or an extensionthereof. A fluid-channeling member threaded to the inner shell isslidably removed from a fluid carrying tube of the supporting column.The magnetic field coil within the hollow space in the innershell andconsistingof turns of hollow conduit insulated from each other has asupporting structure for the housing thereof which is'maintained clampedin place in the electrode column by one or more setscrews which may beloosened. The fluid in and fluid out conduit extensions of the fieldcoil in one embodiment have male fittings brazed to the ends thereof,which fit into spring contact finger assemblies in two tubes in thesupporting column structure, the male fittings carrying O-rings whichprovide fluidtight seals, the spring contact fingers providing goodelectrical connection. The coil and the supporting structure therefor,once the setscrew or screws are loosened, may be removed, carrying withit the male fittings. A new coil. assembly may be thereafter quicklyinserted, the male fittings thereof being slipped into the contactfinger assemblies, the setscrews tightened, and the electrode tipassembly quickly screwed back into position, all in a matter of a fewminutes at most.

In another embodiment, the spring contact finger assemblies are securedto the conduit extensions, and the male fittings are secured to thetubes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional viewshowing the invention according to one embodiment; and

FIG. 2 is a fragmentary view showing a second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, the reference numeral10 generally indicates an electrode supporting column with an extension11 threadably secured thereto and an electrode tip generally designated12 threaded at 18 to the lower end of the extension 1 1. The electrodetip generally designated 12 includes inner and outer shells 13 and 14respectively, each of the shells being annular in shape and generallyU-shaped in cross section, the inside surface of the outer shell beingspaced from the outside surface of the inner shell to form a space 16for tubes providing fluid flow passageways between the shells andextending around the entire tip. The outer shell 14 is threaded at 18 tothe lower end of the extension 11, while the outer shell has an annularrecess 19 around the periphery of the wall of smaller diameter thereofwhich closely fits the adjacent surface 20 of a support andfluid-channeling member generally designated 21 which surface has anannular groove therearound with the O- ring23 seated therein to providefluidtight sealing engagement. The outer shell 14, tubes and inner shell13 are brazed together to form a unit. I

As illustrated the aforementioned space 16 may have therein a pluralityof generally U-shaped tubes peripherally spaced around the entireelectrode tip. Those ends of tubes which lie between the wall of smallerdiameter of the inner shell andthe wall of smaller diameter of the outershell are seen at 25, 26, 27 and '28 respectively extending through anannular passageway 29 in the tip assembly and communicating with anannular passageway 30 which communicates'by way of peripherally spacedannular passageways including 31 and 32 in the support andfluid-channeling member 21, which passageways 31 and 32 communicate withthe interior cavity or chamber 33 of the support member and thence witha fluid passageway 35 formed within the tubular member 36 of thesupporting column. Fluid inlet passageway 35 communicates with fluidinlet means, not shown for convenience of illustration. Preferably thefluid .passageway 35 conducts cooling fluid from the electrode tip. Theoutside ends of tubes 25 and 28 are seen at 39 and 40 respectivelycommunicating with an annular fluid header 41 which communicates with afluid passageway 43 which may be in the form of drilled holes or begenerally cylindrical in shape except that it does not extend around theentire. periphery of the extension 11, a certain peripheral portion ofthe extension 11 being solid and designated 45 and having the bolts 46and 47 therein for reasons to be hereinafter described. It is seen thatthe upper end of the fluid passageway 43 communicates with an additionalannular passageway 48 near the outer wall of the electrode supportingcolumn, the passageway 48.communicating at some point along the axis ofthe electrode or at the upper end of the electrode with fluid inletmeans, not shown for convenience of illustration.

' The aforementioned inner shell 13 is seen to have an extendedannularportion of small diameter 50 which is threaded.

at 38 to an adjacent surface of the support and fluid-channeling membergenerally designated 21, with an O-ring 51 in an annular groove toprovide fluidtight sealing engagement between the inner shell and thewall of the fluid-channeling and support member 21. Because member 21 isthreaded to extension 50 of the inner shell 13, member 21 is slidablyremoved from tube. 36 when the tip assembly is removed by unscrewing at18. It is further seen that the support member 53 for the field coilgenerally designated 54 has an annular groove 56 extending around .theoutside surface thereofiinto which extend a plurality of peripherallyspaced setscrews passing through the wall of the extension generallydesignated 11, one of these setscrews being shown at 58, the setscrewswhen screwed firmly into position extending into the annular groove 56andclamping the field coil support member .53

, housing havingan extended collar portion 65 passing through an opening67 in the support member 53, through which collar portionof the housingpasses one end of the conduit 66 which has a male fitting member 68brazed thereto, the member 68 nestling in the spring contact fingers ofa spring contact finger assembly, two of the fingers being shown at 71and 72 and carrying current to the conduit. The contact member 68 isseen to have annular grooves therein in which are disposed O-rings 73and 74 for providing sealing engagement with the adjacent cylindricalwall of a tubular member 76 composed of conductive material enclosedwithin an outer tube 77 of insulating material.

1 Individual fingers 71 and 72 may culminate in a ring which is threadedor otherwise attached at 104 to tube 76.

It will be understood that the field coil housing 63 has an additionalcollar portion similar to 65, not shown in the plane selected forillustration, passing through an additional opening in support member53, the additional opening not being shown inthe plane selected forillustration, through which additional, collar'portion extends the otherend of the conduit which forms the field coil, the other end of theconduit forming the field coil also having a male contact member similarto 68 but not shown in the plane selected for illustration, which alsomakes contact with an additional spring contact finger assembly, notshown in the plane selected for illustration, and that furtherconductive tube means extends from said other additional contact fingerassembly through the electrode supporting column and communicates withthe terminal of opposite polarity of the source of potential to whichthe aforementioned conductive tube 76 is operatively connected forbringing an energizing current to the field coil, and that also anadditional insulating tube corresponding to insulating tube 77 insulatesthe conductive tube, not shown, from the remainder of the electrodeassembly. In summary, a complete electrical path is provided forbringing energizing current to the field coil, and a complete fluid flowpath is provided for bringing fluid to the field coil, passing saidcooling fluid through the turns of the field coil, and thereafterremoving the fluid and exhausting it through fluid outlet means, notshown for convenience of illustration.

More than two such disconnect assemblies would be required for someparticular configuration.

The slidable relation between tube 36 and tubular portion 80 of supportand fluid-channeling member 21 not only facilitates tip replacement butprovides for differential thermal expansion between the outer wallsurface of the electrode column formed by members 10 and 11 and theinner structure fonning the fluid flow passageway 35; it is seen thatthe outside wall of the aforementioned tubular member 36 is slidablewith respect to the inside wall 79 of the extended annular collarportion 80 of the aforementioned support and fluid-channeling membergenerally designated 21. O-rings 82 and 83 seated in annular grooves inthe wall of tube 36 provide sealing engagement. It is further seen thatthe upper portion of the tube 36 is of generally increased wallthickness and extends into and forms sealing engagement with a tubularextension 84 which may extend up through the remainder of the electrodecolumn and supporting structure.

As previously stated, the support member 53, the field coil housing, andthe field coil are removable as a unit and can be quickly replaced in amatter of minutes at most with a new field coil'which has two conduitextensions similar to extension 66 with. male fittings similarto'fitting'68 adapted to extend into the contact finger assembliesincluding finger assembly generally'designated 70. The finger assembliesand their tubular structures associated therewith must be preciselypositioned radially within the column assembly, and also preciselypositioned peripherally within the column assembly. To this end,insulating plates 88 and 89 are fastened to tube 76 by means of studs 91and insulating tube 77 and insulating split ring 93. The insulatingplate 89 is seen to have an annular collar 95 extending therearoundwhich abuts against an annular shoulder 96 formed in the inside wall ofthe extension generally designated 11; it is also seen that theinsulating plate 89 has an annular wall portion 98 which firmly abutsagainst the adjacent wall of the extension 11, and that the outersurface of the insulating plate 88 abuts against the inside wall 99 ofthe outer cylinder 15 of the column generally designated 10.

The ring member I00 seated in a groove in the outside surface of member15 may be used for supporting an exterior cylindrical heat shieldcomposed'of highly refractory material and preventing the heat shieldfrom slipping down toward the bottom of the electrode.

Support member 53 for thecoil housing and the field coil may be securedto'the field coil housing in any convenient manner. For example, asillustrated in the right-hand portion of the FIG., the support member 53has a portion extending through the annular insulating block 102 andpassing through the upper wall of the coil housing 63 to form clampingmeans. The extended portion is designated 103. Or, member 53 may beattached to member 103 by suitable studs or bolts, not shown.

If desired, alignment pins, not shown for convenience of illustration',may be used in assisting in aligning a new field coil v assembly whenthe assembly is to be inserted in the electrode column. I

Particular reference is made to FIG. 2. The supporting column isgenerally designated 10 and has column extension 11 threaded thereto at17. A fluid passageway is shown at 43 and another at 35, for bringingcooling fluid 'to and from the tip, or vice versa. One conductive tubeis shown at 760 enclosed within insulating sleeve 77a. It will beunderstood that there is anothersimilar electrically insulatedconductive tube extending through the column, the other tube and sleevenot being shown for'conv'enience of illustration. Male fitting 68a issecured to conductive tube 76a at 111 in any convenient manner. Malefitting 68a carries O-rings 73a and 74a in annular grooves to provide afluidtight seal.

Conduit extension 66a extending from insulation 65 has secured theretoat 115 in any convenient manner, as by brazing, a threaded member 118which. has contact finger assembly generally designated 70a threadedthereon at 119. Two of the spring contact fingers are shown at 71a and72a. Thereby, good electrical connection and fluidtight seals are formedbetween the conduit extensions and the conductive tubes.

Alignment pins may be used if desired, as explained in connection withFIG. 1.

Whereas the quick disconnect feature has been described with referenceto -a field coil used in an electrode, our invention includes meansutilizing a fluid flow and a current flow, adapted to be quicklyconnected to and quickly disconnected from means bringing fluid to andother means conducting fluid from the utilization means, the meansbringing fluid to and the other means conducting fluid from also formingelectrical circuit means for bringing a current to the utilizationmeans.

We claim as our invention:

1. An electrode having a supporting column including two contact fingerassemblies and two conductive tubes terminating in the contact fingerassemblies respectively, the two conductive tubes forming a fluid inletand a fluid outlet respectively, the two conductive tubes being adaptedto be connected to terminals of opposite polarity respectively of asource of potential: a field coil assembly including a coil housing, acoil support member secured to said housing, the coil support memberbeing removably mounted in position in the supporting column, a fieldcoil of hollow conduit with ends extending through the support member,and two male fittings on the ends of the conduit removably inserted inthe contact finger assemblies of the supporting column and formingsealing engagement therewith and electrical contact therewith.

2. A field coil assembly according to claim 1 in which the supportingcolumn is additionally characterized as having a substantially centrallylocated fluid-carrying tube extending therethrough, and the field coilassembly includes in addition a hollow annular electrode tip enclosingthe field coil housing on the bottom and sides thereof, the tip beingremovably threaded to the adjacent end of the supporting column, and afluid-channeling and support member threadedly secured to the tip andslidably inserted over the outside of the fluid-carrying tube of thesupporting column.

3. A field coil assembly according to claim 2 in which the tip isadditionally characterized as having a fluid flow passageway thereinnear the arcing surface, said fluid flow passageway communicating withthe fluid-carrying tube of the supporting column while the'tip isattached thereto, said electrode supporting column being additionallycharacterized as having an outer cylindrical wall with a fluidpassageway therein communicating with the fluid flow passageway in thetip while the tip is attached to the supporting column.

4. A quick-change field coil assembly according to claim 1 including inaddition a hollow annular shell generally U- shaped in cross sectionhaving the field coil housing disposed therein, the shell beingremovably threaded to the column and enclosing the coil housing on thebottom and both sides thereof.

5. A quick-change field coil assembly according to claim 1 including inaddition a plurality of setscrews extending through the wall of thesupporting column for clamping the coil support member in positionwithin the column and holding the field coil conduit and said malefittings aligned with the contact finger assemblies.

6. In combination, an electrode supporting column and a quick-changefield coil assembly of the type in which a hollow conduit forms theturns of the coil, a housing for the coil, said turns being electricallyinsulated from each other, the ends of the conduit extending through thefield coil housing and having connected thereto tubular male contactmembers detachably engaging contact finger assemblies and making sealingengagement with the inside walls of conductive tubular memberselectrically connected to the contact fingers, and adapted for use in anelectrode having a fluid-cooled electrode tip arinular in shape andgenerally U-shaped in cross section in which tip the field coil andfield coil housing are disposed, the electrode including a columnassembly having a pair of contact finger assemblies connected toconductive tubes adapted to be electrically connected to terminals ofopposite polarity of a source of potential to supply an energizingcurrent to the coil and adapted to be connected to fluid inlet and fluidoutlet means for bringing a cooling fluid to the coil, passing saidfluid through the turns of the coil and thereafter exhausting the fluidfrom the electrode, the quick-change field coil assembly including aninsulating housing and a magnetic field coil therein composed of hollowconductive conduit, the ends of the conduit extending from the housingand having male contact members secured thereto, the male contactmembers being removably inserted into the contact finger assemblies ofthe electrode column assembly and making electrical connectiontherewith, the male contact members while inserted in the conductivetubes of the column assembly making fluidtight sealing engagementtherewith.

7. A quick-change field coil assembly according to claim 6 including inaddition an annular mounting member secured to the upper end of thefield coil housing, said field-coil-mounting member having a pair ofpassageways therethrough through which the ends of the conduit extend,the field-coilmounting member being generally annular in shape andclosely fitting the inside wall of the electrode column assembly therebybeing secured therein and mounting the field coil in position within thetip.

8. A quick-change field coil assembly according to claim 7 including inaddition a plurality of peripherally spaced setscrews passing throughthe wall of the column assembly and in which the mounting member isadditionally characterized as having an annular groove extendingtherearound for removably receiving ends of the plurality ofperipherally spaced setscrews to hold the field coil securely inposition.

9. A field coil assembly according to claim 6 including in addition ahollow shell of conductive material generally annular in shape andgenerally U-shaped in cross section having the field coil and field coilhousing mounted therein, the shell having means secured theretoextending into the column as sembly with a passageway within the shellforming a fluid flow passageway for the flow of cooling fluid to coolthe electrode tip.

10. A field coil assembly according to claim 8 including in additionmeans for clamping the electrode housing and the shell in positionwithin the electrode column.

11. A quick-change field coil assembly according to claim 10 in whichthe means for securing the field coil and field coil housing within thecolumn assembly includes an annular mounting member secured to the fieldcoil housing, the inner cylindrical wall of the column having a portionwhich abuts against the member, and including in addition means forclamping the support member and the abutting portion against supportingstructure of the electrode column.

12; A quick-change field coil assembly according to claim 11 in whichthe member is additionally characterized as having an annular groovearound the outside thereof for receiving the ends of a plurality ofperipherally spaced setscrews extending through the wall of theelectrode column supporting structure and extending into said groove toclamp the field-coilsupporting member in position within the electrodetip.

13. In an electrode, in combination, a supporting column and removablemeans forming an arcing surface, the supporting column including twotubes composed of electrically conductive material extending at least aportion of the length of the column and electrically insulated from eachother, a detachable field coil assembly including a fluid-cooledmagnetic field coil and two coil extensions extending toward the twotubes and substantially aligned with the two tubes respectively when thecoil assembly is inserted in the electrode, and means secured to each ofthe tubes adapted to make good electrical connection with other meanssecured to each of the coil extensions when the coil assembly isinserted and to form sealing engagement therewith with a fluid passageopening between tube and extension.

14. Apparatus according to claim 13 wherein the means secured to each ofthe tubes is a spring contact finger as sembly, and the means secured toeach of the coil extensions is a fitting adapted to be engaged by thefingers of the associated contact finger assembly.

15. Apparatus according to claim 14 wherein each fitting has at leastone annular groove therein, and an O-ring seated in the annular grooveproviding said sealing engagement.

16. Apparatus according to claim 13 wherein the means secured to each ofthe coil extensions is a spring contact finger assembly, and the meanssecured to each of the tubes is a fitting adapted to be engaged by thefingers of the associated contact finger assembly.

17. Apparatus according to claim 16 wherein each fitting has at leastone annular groove therein, and a O-ring seated in the annular grooveproviding said sealing engagement.

18. In an electrode, in combination, a supporting column and removablemeans fonning an arcing surface, the supporting column including twotube means composed of electrically conductive material extending atleast a portion of the length of the column and electrically insulatedfrom each other, a detachable field coil assembly including afluid-cooled magnetic field coil and two coil extensions extendingtoward the two tube means and substantially aligned with the two tubemeans respectively when the coil assembly is inserted in the electrode,and two spring contact finger assemblies secured to the two coilextensions respectively near the ends thereof, the last-named means andthe contact finger assemblies ineach of the'two tube meal mcludmg meanson the ends cludes means for forming a fluidtight seal to prevent thethereof adjacent the contact finger assemblies adapted to be firmlyengaged by the fingers of the contact finger assemblies and to make goodelectrical connection therewith.

19. Apparatus according to claim 18 wherein at least one of escape offluid flowing through the tube means and thecoil extensions.

1. An electrode having a supporting column including two contact fingerassemblies and two conductive tubes terminating in the contact fingerassemblies respectively, the two conductive tubes forming a fluid inletand a fluid outlet respectively, the two conductive tubes being adaptedto be connected to terminals of opposite polarity respectively of asource of potential: a field coil assembly including a coil housing, acoil support member secured to said housing, the coil support memberbeing removably mounted in position in the supporting column, a fieldcoil of hollow conduit with ends extending through the support member,and two male fittings on the ends of the conduit removably inserted inthe contact finger assemblies of the supporting column and formingsealing engagement therewith and electrical contact therewith.
 2. Afield coil assembly according to claim 1 in which the supporting columnis additionally characterized as having a substantially centrallylocated fluid-carrying tube extending therethrough, and the field coilassembly includes in addition a hollow annular electrode tip enclosingthe field coil housing on the bottom and sides thereof, the tip beingremovably threaded to the adjacent end of the supporting column, and afluid-channeling and support member threadedly secured to the tip andslidably inserted over the outside of the fluid-carrying tube of thesupporting column.
 3. A field coil assembly according to claim 2 inwhich the tip is additionally characterized as having a fluid flowpassageway therein near the arcing surface, said fluid flow passagewaycommunicating with the fluid-carrying tube of the supporting columnwhile the tip is attached thereto, said electrode supporting columnbeing additionally characterized as having an outer cylindrical wallwith a fluid passageway therein communicating with the fluid flowpassageway in the tip while the tip is attached to the supportingcolumn.
 4. A quick-change field coil assembly according to claim 1including in addition a hollow annular shell generally U-shaped in crosssection having the field coil housing disposed therein, the shell beingremovably threaded to the column and enclosing the coil housing on thebottom and both sides thereof.
 5. A quick-change field coil assemblyaccording to claim 1 including in addition a plurality of setsCrewsextending through the wall of the supporting column for clamping thecoil support member in position within the column and holding the fieldcoil conduit and said male fittings aligned with the contact fingerassemblies.
 6. In combination, an electrode supporting column and aquick-change field coil assembly of the type in which a hollow conduitforms the turns of the coil, a housing for the coil, said turns beingelectrically insulated from each other, the ends of the conduitextending through the field coil housing and having connected theretotubular male contact members detachably engaging contact fingerassemblies and making sealing engagement with the inside walls ofconductive tubular members electrically connected to the contactfingers, and adapted for use in an electrode having a fluid-cooledelectrode tip annular in shape and generally U-shaped in cross sectionin which tip the field coil and field coil housing are disposed, theelectrode including a column assembly having a pair of contact fingerassemblies connected to conductive tubes adapted to be electricallyconnected to terminals of opposite polarity of a source of potential tosupply an energizing current to the coil and adapted to be connected tofluid inlet and fluid outlet means for bringing a cooling fluid to thecoil, passing said fluid through the turns of the coil and thereafterexhausting the fluid from the electrode, the quick-change field coilassembly including an insulating housing and a magnetic field coiltherein composed of hollow conductive conduit, the ends of the conduitextending from the housing and having male contact members securedthereto, the male contact members being removably inserted into thecontact finger assemblies of the electrode column assembly and makingelectrical connection therewith, the male contact members while insertedin the conductive tubes of the column assembly making fluidtight sealingengagement therewith.
 7. A quick-change field coil assembly according toclaim 6 including in addition an annular mounting member secured to theupper end of the field coil housing, said field-coil-mounting memberhaving a pair of passageways therethrough through which the ends of theconduit extend, the field-coil-mounting member being generally annularin shape and closely fitting the inside wall of the electrode columnassembly thereby being secured therein and mounting the field coil inposition within the tip.
 8. A quick-change field coil assembly accordingto claim 7 including in addition a plurality of peripherally spacedsetscrews passing through the wall of the column assembly and in whichthe mounting member is additionally characterized as having an annulargroove extending therearound for removably receiving ends of theplurality of peripherally spaced setscrews to hold the field coilsecurely in position.
 9. A field coil assembly according to claim 6including in addition a hollow shell of conductive material generallyannular in shape and generally U-shaped in cross section having thefield coil and field coil housing mounted therein, the shell havingmeans secured thereto extending into the column assembly with apassageway within the shell forming a fluid flow passageway for the flowof cooling fluid to cool the electrode tip.
 10. A field coil assemblyaccording to claim 8 including in addition means for clamping theelectrode housing and the shell in position within the electrode column.11. A quick-change field coil assembly according to claim 10 in whichthe means for securing the field coil and field coil housing within thecolumn assembly includes an annular mounting member secured to the fieldcoil housing, the inner cylindrical wall of the column having a portionwhich abuts against the member, and including in addition means forclamping the support member and the abutting portion against supportingstructure of the electrode column.
 12. A quick-change field coilassembly according to claim 11 in which the member is additionallycHaracterized as having an annular groove around the outside thereof forreceiving the ends of a plurality of peripherally spaced setscrewsextending through the wall of the electrode column supporting structureand extending into said groove to clamp the field-coil-supporting memberin position within the electrode tip.
 13. In an electrode, incombination, a supporting column and removable means forming an arcingsurface, the supporting column including two tubes composed ofelectrically conductive material extending at least a portion of thelength of the column and electrically insulated from each other, adetachable field coil assembly including a fluid-cooled magnetic fieldcoil and two coil extensions extending toward the two tubes andsubstantially aligned with the two tubes respectively when the coilassembly is inserted in the electrode, and means secured to each of thetubes adapted to make good electrical connection with other meanssecured to each of the coil extensions when the coil assembly isinserted and to form sealing engagement therewith with a fluid passageopening between tube and extension.
 14. Apparatus according to claim 13wherein the means secured to each of the tubes is a spring contactfinger assembly, and the means secured to each of the coil extensions isa fitting adapted to be engaged by the fingers of the associated contactfinger assembly.
 15. Apparatus according to claim 14 wherein eachfitting has at least one annular groove therein, and an O-ring seated inthe annular groove providing said sealing engagement.
 16. Apparatusaccording to claim 13 wherein the means secured to each of the coilextensions is a spring contact finger assembly, and the means secured toeach of the tubes is a fitting adapted to be engaged by the fingers ofthe associated contact finger assembly.
 17. Apparatus according to claim16 wherein each fitting has at least one annular groove therein, and aO-ring seated in the annular groove providing said sealing engagement.18. In an electrode, in combination, a supporting column and removablemeans forming an arcing surface, the supporting column including twotube means composed of electrically conductive material extending atleast a portion of the length of the column and electrically insulatedfrom each other, a detachable field coil assembly including afluid-cooled magnetic field coil and two coil extensions extendingtoward the two tube means and substantially aligned with the two tubemeans respectively when the coil assembly is inserted in the electrode,and two spring contact finger assemblies secured to the two coilextensions respectively near the ends thereof, each of the two tubemeans including means on the ends thereof adjacent the contact fingerassemblies adapted to be firmly engaged by the fingers of the contactfinger assemblies and to make good electrical connection therewith. 19.Apparatus according to claim 18 wherein at least one of the last-namedmeans and the contact finger assemblies includes means for forming afluidtight seal to prevent the escape of fluid flowing through the tubemeans and the coil extensions.